btrfs-progs: fix double file descriptor close in cmd_replace_start()

Reported by 'gcc -fanalyzer':
cmds/replace.c:357:17: warning: double ‘close’ of file descriptor ‘fdmnt’ [CWE-1341] [-Wanalyzer-fd-double-close]

The first close is done right before going to the label
'leave_with_error' but the variable is not reset to -1 so in the exit
block close() is called again.

Signed-off-by: David Sterba <dsterba@suse.com>

cmds/replace.c

@@ -199,7 +199,6 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 	if (ret != 0) {
 		if (ret < 0)
 			error("unable to check status of exclusive operation: %m");
-		close(fdmnt);
 		goto leave_with_error;
 	}